Mystery Baby in The Sims 3?

So I was checking in on some families while I was playing The Sims 3. And as I was doing this something happened, problem is, I don't know what that "something" is. I went back to my favorite (or "main") household after checking on those few, and I noticed something really odd. Okay, so far the household has only had one member, who is A MAN (this is important information), we'll call him Jack Smith. And now, there is a second family member. A baby boy that has the same last name as Jack (we'll call him Bobby Smith). See Bobby recognizes Jack as his father, but he doesn't recognize anyone as his mother. No one at all. He recognizes his Father, and his half-siblings. No one else.

How did Bobby come to be?! Was Jack abducted by aliens and impregnated? The baby isn't green, so I'm not sure. Did Jack bone the maid? Maybe, but why would the baby live with Jack and have his last name? There's a female ghost haunting Jack's house, who I had him WooHoo with a while back. Is Bobby the son of Jack and the ghost? Is that even possible?!

Any help at all would be greatly appreciated.